This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A myriad of studies have identified that people with medial knee OA (MKOA) typically have weak quadriceps femoris muscles, excessive knee adduction moments and excessive mediolateral joint laxity all of which can contribute to erosion of cartilage in the knee. However, other than quadriceps strengthening programs, there is a dearth of rehabilitation strategies that have shown marked improvement of joint function. The long term goal of this work is to develop patient specific rehabilitation programs to help improve function while reducing the progression of MKOA. The goal of the proposed work is to understand how quadriceps strength, knee stiffness, proprioception and instability contribute to disease progression and if medial muscle co-contraction is a strategy that will reduce or exacerbate the progression of OA. The knowledge gained in the study will allow us to understand which modifiable characteristics (knee stiffness and instability, and medial muscle co-contraction) will improve knee function without further joint damage and to develop screening tools that properly identify patients who will benefit from the rehabilitation programs. Dr. Buchanan will serve as scientific mentor and Dr. Snyder-Mackler will be career mentor.